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agent75

Motronic 1.3 computer - manual 325i

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I have a late manual (yesss) 325i (yessss) parts car which I want to start and annoy my neighbours with before stripping it.  The car turns over and I feel I have done all of the tests possible and I have narrowed it to the motronic 1.3 computer (grey label..173 ).  it switches the main relay on but that's about it.  no check engine light on dash and all of the same lights on dash light no matter if computer is connected or not.  It won't perform the stomp test.  it won't even switch the fuel pump relay.  Looks like a bit of H2O may have leaked in to it at some point but the board looks perfect and in unaffected. In short, does anyone have a good computer I could buy or borrow to rule this out?  I'll be selling a few parts off this soon too so don't hesitate to ask. 

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Hold the phone! Crank pos sensor is open circuit! That could be it! I'll get a replacement and see how i go. I'd still be interested to see if any computers are out  there

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Well well, there you go then. It was the crank position sensor. Started up first pop and sounds good. Very happy. Going to put a steering wheel on it and take her for a spin. No need for computer now thank you.

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Good stuff getting it sorted! So the sensor was just bad?

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Yes, the e30 m40 and m20 crank sensors should show 500-600 ohms across two pins. Mine was open circuit. I Jerry rigged my known good one from my 318 and baboom! Note that the later sensors on m52 and m54 i think are hall effect sensors and don't show same readings as i tried testing these as a comparison and they read like a failed e30 vr sensor

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